Geocomposite liners are well known for the purpose of containment of materials. In particular, geocomposite clay liners (GCL's) offer engineers the designability to achieve permeability properties equal to the placement of two-to-three feet of clay in containment applications with approximately one-quarter inch of material. The use of such geocomposite clay liners serves to significantly increase storage space. In conventional applications, these geocomposite clay liners are placed over a subgrade in the containment area. After these geocomposite liners are placed over the subgrade, a fill material may be placed over the outer surface of the geocomposite liner.
Conventional geocomposite clay liners use contaminant resistant sodium bentonites which are encapsulated between two layers of a polypropylene geotextile. The upper geotextile is a non-woven needle punched fabric designed to assure maximum strength and confinement of the clay in a hydrated state, while allowing sufficient liquid penetration to assure intimate contact when used in conjunction with a geomembrane. The geotextile used on the bottom side of the liner is a woven, slit-film material manufactured to optimize both the internal shear strength of the finished product and its friction angle with the soils below.
In normal use, the conventional geocomposite clay liner will include a first fibrous layer, a second fibrous layer, and a sodium bentonite material therebetween. The needle punched top layer will have fibers extending upwardly and into the upper woven material. These fibers will extend outwardly of the woven bottom layer. The use of this needle punching serves to create a mechanical non-adhesive containment of the bentonite between the layers.
Unfortunately, when such a geocomposite clay liner is placed on the subgrade, the shear forces applied to the GCL will cause the upper fibrous layer to separate from the lower fibrous layer. There are three fundamental reasons for the separation of the upper and lower layers. First, the high shear forces that can be applied to the liner during installation and use can force the separation of the layers. Secondly, the sodium bentonite, when wet, acts as a lubricant between the layers. This lubricant-type action facilitates the movement of one layer with respect to the other layer. Thirdly, the use of the needle punching does not provide any true resistance to the separation of the layers. The needle punching is carried out for the purpose of the containment of the bentonite between the layers. The ends of the needle punched fibers extend freely outwardly of the lower woven layer. As such, when slippage occurs between the layers, the ends of the fibers offer no resistance to this separation.
It is an object of the present invention to provide a geocomposite liner that effectively resists slippage between the layers.
It is another object of the present invention to provide a geocomposite liner that withstands shear forces placed upon the liner material in actual installation and use.
It is a further object of the present invention to provide a geocomposite liner that effectively contains the sodium bentonite (or related material) between the outer layers.
It is still another object of the present invention to provide a geocomposite liner that is easy to manufacture, easy to use, and easy to install.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.